The present invention relates to flow coating articles with a viscous, plastic coating using a plurality of nozzles, and more particularly, to a device and method for eliminating the drippage of excess material from such nozzles.
Flow coating of various articles of manufacture with polymeric resin or other coating material has become more widespread during the past few years. For example, flow coating processes have been used to coat such diverse articles as glass containers, as taught by Waugh, U.S. Pat. No. 4,092,953; plywood surfaces, as taught by Fraatz, U.S. Pat. No. 3,431,889; substrates such as steel, wood, hardboard, aluminum and the like, as taught by Hanson, U.S. Pat. No. 3,725,112; and foil substrates in the production of decorative emblems as disclosed in copending application Ser. No. 903,829, filed May 8, 1978.
For many, if not all, of the above coating procedures, it is necessary that the coating thickness be closely controlled and that the coating be laid down with no surface discontinuities. But, because the plastic coating material is in a liquid state during the coating procedure, the residual material in the applicator nozzles has a tendency to drip from the tips of these nozzles even after flow has been shut off. This not only wastes plastic material but also causes surface discontinuities on the coated article.
Accordingly, there is a need in the art for a process and apparatus whereby flow from the applicator nozzles of a plastic flow coating device may be terminated accurately and without drippage.